feat(replay): add framebuffer hashing and snapshots

src/Chip8.Replay/FramebufferHash.cs

@@ -0,0 +1,59 @@
+using System.Globalization;
+using Chip8.Core;
+
+namespace Chip8.Replay;
+
+public static class FramebufferHash
+{
+    const ulong fnvOffsetBasis = 14695981039346656037UL;
+    const ulong fnvPrime = 1099511628211UL;
+
+    public static ulong compute(Machine machine) => compute(FramebufferSnapshot.capture(machine));
+
+    public static ulong compute(FramebufferSnapshot snapshot)
+    {
+        ulong hash = fnvOffsetBasis;
+        hash = mix(hash, (byte)(snapshot.width & 0xFF));
+        hash = mix(hash, (byte)((snapshot.width >> 8) & 0xFF));
+        hash = mix(hash, (byte)(snapshot.height & 0xFF));
+        hash = mix(hash, (byte)((snapshot.height >> 8) & 0xFF));
+        foreach (byte color in snapshot.colors)
+        {
+            hash = mix(hash, color);
+        }
+        return hash;
+    }
+
+    public static ulong computeWithRegisters(Machine machine)
+    {
+        ulong hash = compute(machine);
+        foreach (byte register in machine.v)
+        {
+            hash = mix(hash, register);
+        }
+        hash = mix16(hash, machine.i);
+        hash = mix16(hash, machine.pc);
+        hash = mix(hash, machine.sp);
+        hash = mix(hash, machine.delayTimer);
+        hash = mix(hash, machine.soundTimer);
+        return hash;
+    }
+
+    public static string toHex(Machine machine) => format(compute(machine));
+
+    public static string format(ulong hash) => hash.ToString("X16", CultureInfo.InvariantCulture);
+
+    static ulong mix(ulong hash, byte value)
+    {
+        hash ^= value;
+        hash *= fnvPrime;
+        return hash;
+    }
+
+    static ulong mix16(ulong hash, ushort value)
+    {
+        hash = mix(hash, (byte)(value & 0xFF));
+        hash = mix(hash, (byte)((value >> 8) & 0xFF));
+        return hash;
+    }
+}